Light-correction system for printers of colour cinematographic films

ABSTRACT

A light-correction system for cinematographic colour film printers which operate on the additive three-colour principle. Electric pulses, originating in binary form from a reader of a perforated programming tape on which information relating to desired corrections is stored, are converted for each of the three primary colours by a digital-analogue arrangement into a representative electric voltage, and the opening of each of three corresponding flux modulators is controlled by a respective electric motor which is supplied with the respective voltage through a position-control potentiometric assembly. Each of the flux modulators includes a cam for converting rotation of the corresponding motor into angular displacement of a pivoting member mounted for rotation on an operating shaft of an aperture shutter of the respective modulator.

O Umted States Patent 11 1 1111 3,752,577 Grossetete et a1. Aug. 14,1973 [54] LIGHT-CORRECTION SYSTEM FOR 3,576,370 4/1971 Kuhn et a1.355/36 X PRINTERS 0F COLOUR 3,602,579 3/ 1971 Silvertooth 355/36 XCINEMATOGRAPHIC FILMS 3,642,377 2/1972 Young 355/88 [75] Inventors:Roger Grossetete, Yerres; Jean primary Examine, Samue] s Matthews PiemBlaublomme, Pans both of Assistant Examiner-E. M. Bercl FranceAttorney-Alan H. Levine [73] Assignee: Etablissements Andre Debrie,Paris,

France [57] ABSTRACT 22 Filed: Nov. 15 1971 A light-correction systemfor cinemato raphic colour 1 1 3 8 film printers which operate on theadditive three- [21] Appl' 198590 colour principle. Electric pulses,originating in binary form from a reader of a perforated programmingtape [30] Foreign Application Pri rit D t on which information relatingto desired corrections is Dec. 16 1970 France 7045353 med, are each thePlimary ours by a digital-analogue arrangement into a represen- 52 u.s.c1 355/36 355/34 355/83 alive elem and Penin8 each 511 Im. c1. 0031327/76 mslmdin! flux "mdulatm is by a 58 Field of Search 355/34 35 36 83spective elem whih is suPPied with the spective voltage through aposition-control potentiometric assembly. Each of the flux modulatorsincludes [56] References Cited a cam for converting rotation of thecorresponding motor into angular displacement of a pivoting memberUNITED STATES PATENTS mounted for rotation on an operating shaft of anaper- 3,552,852 1/1971 Sternke et a1. 355/35 me Shutter f the respectivemodulamn 3,517,996 6/1970 Jones 355/83 X 3,519,347 7/1970 Bowker et a1355/83 X 4 Claims, 3 Drawing Figures DELAY) TRIGGEIR Mo R0 Bo 'l E? ;I/1 Sa i- [SELECTOR MEMORY/CONVERTER MEMORY CONVERTER H3 I C3 CONVERTERMEMORY P IENIEnws 14 m5 3. 752,577

sum 1 0r 2 Fig.1

MEMORY) DELAY} TR|GGER I N Ho R0 Bo W p a ff SELECTOR {MEMORY/CONVERTERMEMORY \CONVERTER H3 I C3 CONVERTER MEMORY /NVENTOR$: ROGGRq-leosse'rev'z Ji PIERRE BmuaLonnE PATENTED AUG 14 I975 SHEET 2 OF 2LIGHT-CORRECTION SYSTEM FOR PRINTERS OF COLOUR CINEMATOGRAPHIC FILMSBACKGROUND OF THE INVENTION The present invention relates to optical orcontact printing machines for use with colour cinematographic films, andis concerned more particularly with a lightcorrection system which makesit possible to obtain copies exhibiting desired effects on projectionfrom a given original. This system is applicable more particularly toprinting machines operating by the additive three-colour principle.

The aforesaid process involves splitting up the light flux emitted by alight source, such as an incandescent or halogen lamp, into threemonochromatic parallel beams each corresponding to one of the primarycolours (red, green, blue). The light flux is split up by means ofasystem of filtering foils or'reflecting mirrors. Each of these threebeams passes through a flux modulator which is adapted to cause theintensity of the beam to vary as a function of a prestablishedinstruction programme. The three beams are then recombined into a singlelight beam by a system of foils and reversing mirrors, the spectralcomposition'of which can thus be modified at will with respect to thatof the initial beam. This recombined beam serves to illuminate theimages of the original film in succession to provide for the productionof an optical or contact copy.

The desired intensity variations are determined from a previousprojection of the original with a suitable grading device whichestablishes the different intensity variations for the various sequencesof the film in question. In practice, the information obtained by thegrading device is stored in coded form on a programming tape having sixperforated tracks in accordance with the binary numbering system. Thesesix perforated tracks thus make it possible to establish a total of 50bits of information each corresponding to one adjustment step in theaperture of the respective flux modulator for each of the three primarycolours. The aperture variation causes a suitable variation in theintensity of light leaving each modulator.

The printing of the copies is effected using the information carried bythe programming tape. The tape advances step-by-step with each change infilm sequence in a suitable reader. The reader is provided withoutcontacts which are closed or open depending on whether there is aperforation on the corresponding track and for the colour underconsideration or not. In the systems as known at present, the use of theinformation thus translated into electric pulses is dependent onelectromagnetic relay systems which operate as many cams as there aretracks on the programming tape, (six in the present instance). Thesecams are of progressively increasing height and their deviation istotalised to act mechanically on an iris or blade-type arrangement,which modulates the light beam of the primary colour in question.

These known systems have various disadvantages from thepoint of view ofweight, size, cost inertia and reliability, and it is the purpose of thepresent invention to overcome these disadvantages.

SUMMARY OF THE INVENTION According to the present invention there isprovided a process for adjusting a light-correction system of acinematographic colour film printing machine which operates on theadditive three-colour principle in which the light flux emitted by asource is split up into three monochromatic beams which are each passedthrough the flux modulator and thereafter recombined, the processcomprising the steps of, recording correction information on aperforated programming tape. advancing the tape step-by-step with theadvance of the film being printed, extracting the information from thetape in the form of electric pulses with a tape reader, converting theinformation for each of the said monochromatic beams with adigital-analogue arrangement into a respective electrical voltage, andsupplying an electric motor which is connected to an aperturecontrolling device on the corresponding flux moudlator with theaforesaid voltage through a positioncontrolling potentiometric assembly.

The present invention also provides a lightcorrection system for acinematographic colour film printing machine which is adapted to operateon the additive three-colour principle in which the light flux emittedby a source is split up into three monochromatic beams which are eachpassed through a flux modulator and thereafter recombined, the systemcomprising, means for advancing a perforated programming tape on whichcorrection information is recorded step-by-step with the advance of afilm to be printed, a programming tape reading adapted to produce anoutput of electric pulses a digital-analogue arrangement adapted toconvert the pulses relating to each of the said monochromatic beams intoa representative electrical voltage, and means for separately adjustingthe aperture of each of the flux modulators, and electric motorconnected to each of the said adjusting means, and aposition-controlling potentiometric assembly adapted to supply the motorwith the said voltage.

In a preferred embodiment of the present invention, the adjustment ofthe aperture of the flux modulator is deferred with respect to theinformation stored on the programming tape and is triggered by areference notch or index carried by the film so as to be produced in theinterval of a change in sequence. To this end, the rotation of thecontrolling electric motor is converted into an angular displacement ofa pivoting member mounted for rotation on the operating shaft of theclosure shutter or shutters of the flux modulator, and this operatingshaft is only made fast angularly with the one said pivoting memberduring a short time period which is within the interval of the change insequence.

According to another feature of the invention, the angular interlockingof the said pivoting member with the operating shaft of the closureshutter or shutters is controlled, against the action of a returnspring, by an electromagnet receiving an electric pulse indicative of achange in sequence. The use of the information output of the reader ofthe programming tape is thus to some degree prepared for by the electricmotor and the associated position control system, while the effectiveuse thereof is deferred until the precise instant of a change insequence of the film.

Other features and advantages of the invention will be apparent fromreading the following description of one embodiment, with reference tothe accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a simplified electriccircuit diagram of a light-correction system according to the invention,only one of the three light flux modulators being shown;

FIG. 2 and 3 are longitudinal and transverse sections, respectively of aflux modulator.

DESCRIPTION OF AN EMBODIMENT OF THE INVENTION The system forelectrically controlling the flux modulators, as shown diagrammaticallyin the form of a block diagram in FIG. 1, comprises firstly a regulatedelectric supply system (not shown), and a means for controlling theadvance of the programming tape and the deferred use of the informationstored by it, said means comprising an order-initiating memory Moperated by a reference index or notch carried by the original film atthe location of each change in sequence, a delay arrangement R designedto take into accountthe distance between the index-sensing device of thepreceding memory and the projection-aperture, a monostable triggeringdevice B controlled by the signal as thus deferred, a pulse emitter Einitiated by the' said triggering device, and a step selector 5,,switching the pulses received from the preceding emitter in successiontowards each of the three circuits associated with the flux modulators.

The control system additionally comprises three individual controlcircuits, each associated with one of the flux modulators correspondingto the three primary colours. Each of these circuits comprises a memoryM M or M; of convention design, the inputs of which are directlyconnected to the track-contacts of the programming tape reader L, aswell as a digital-analogue converter C C or C which is adapted totranslate the information received in the form of a binary signal fromthe associated memory into a proportional continuous electric voltage.The three memories M M and M are controlled by the step or spacingselector S, which sequentially controls their opening, and also by aclearing circuit (not shown). The essential purpose of these memories isto record the information received from the programming tape reader Lwith each advance of this latter and to keep the information availv ableat the input of the associated converters as long as is necessary foruse of the recured information.

The information established in analogue form by the converters C C, andC is translated into intensity variations of the monochromatic fluxes byflux modulators the position of which are servo-controlled. A fluxmodulator is illustrated diagrammatically in FIG. 1.

The light flux modulator comprises a rigid housing 1 into the upperportion of which two aligned circular windows 2 and 2 are drilled. Twosymmetrical opaque shutter members 3 and 3' are disposed between thewindows keyed on two parallel and spaced rotating shafts. Thedisplacements of the two shutters are synchronised and take place inopposite directions, so that they offer an aperture of variable surfacearea to the passage of light beams (shown shaded in FIG. 3).Consequently, they intercept a larger or smaller fraction of thc'lightflux admitted through the windows 2 and 2'. The closure shutter 3 ismore specifically fixed to the end of a hollow shaft 4 journalling bymeans of ballbearings in a reinforced wall of the housing 1. The hollowshaft 4 also carries at the same end a member 5 machined in the form ofa cam having re-entrant surfaces, and also a toothed wheel 6 adapted tomesh with as little play as possible with an identical toothed wheel 6keyed on the shaft of the other shutter 3', the shaft wheels thus makingthe rotational movements of these two shutters synchronised as alreadymentioned above. At its opposite end, the hollow shaft 4 carries acircular plate 7 forming a brake element. Arranged coaxially with thehollow shaft 4 is a sliding rod 8 which is rigidly attached to a plunger9 of an electromagnet 10. In the absence of energisation of the controlwinding, the plunger is biased by the action of a spring out of thecoil, in which position it comes into contact with the circular plate 7and thus by friction immobilises the hollow shaft 4 in the angularposition which it, has reached whenthe plunger contacts the plate 7. Therod 8 carries a stop or abutment collar 11 at its free end. The end of apivoting blade 13 is held against the stop 11 by the action of acompression spring 12. The pivoting blade 13 is connected at its otherend by a fork joint to the cranked end of a lever 14 which is mountedfor pivotal movement by means of a roller bearing on the hollow shaft4.The blade 13 is provided at its upper end with a pair of aligned lateralprojections which support rollers 15 and 15' which are adapted to engagethe re-entrant surfaces of the cam 5, but which are normally heldspac'ed from-these surfaces by the action a blade return spring 12. Thedisplacements of the pivoting lever 14 are controlled by a directcurrent electric motor 16 via a speed reduction gear by meansof arotatable cam 18 keyed on the motor shaft 17 and a roller 19 mounted onthe pivoting lever and held in contact with the cam by a tension spring20. A slide member of a position control potentiometer 21 is keyed onthe shaft 17.

It is apparent from the foregoing description that the shutters 3 and 3'remain locked in the position because of the braking action exerted bythe plunger 9 of the electromagnet 10 on the circular plate 7 which isrigidly mounted on the hollow shaft 4. However, this does not preventthe motor 16 from responding to information received by a rotationalmovement which causes a pivoting in one direction or the other of thelever 14 and of the blade 13 which is associated'with it. The angularposition of the rollers Is and 15 ceases for this reason to be incoincidence with that of the re-entrant surfaces ofthe carn 5. The motor16 is thus prepared to act on the information received, under thecontrol of the position-control potentiometer 21, but it will only do sowhen thevcoil of the electromagnet 10 is placed under voltage. Actually,at this particular moment, the pull of the plunger 9 will simultaneouslyhave the effect of freeing the circular plate 7 from the brakingpressure exerted on it and of causing, by means of the rod 8 and thestop collar 11 acting on the free end of the blade 13, the engagement ofthe rollers 15 and 15' carried by this latter with the re-entrantsurfaces of the cam 5. The cam 5 will then itself pivot in such a way asto re-align its angular position with that of the rollers, thus drivingwith it the shutters 3 and 3'. The resultant change in shutter spacingwill thus be dependant on the information received from the programmingtape for the primary colour in question. It will be appreciated that theinertia of the movable equipment Referring for the time being to FIG. 1of the accompanying drawings, the electrical control means of the fluxmodulator comprises essentially two circuits. The first, which controlsthe operationof the electromagnet 10, transmits to the latter, throughan amplifier A a suitable deferred electric control pulse having asufficiently short duration (for example, m8), so that the execution ofthe desired correction takesgplace in the interval separating the firstimage of thetsequence in question of the film from the last image of thepreceding sequence. The second circuit, which is associated with themotor 16, comprises a potentiometric assembly 22 which is acted upon bythe digital-analogue converter C through an amplifier A,, an amplifier Aof similar form but having a gain equal to the unit being introduced forthe purpose of correction of thermal deviation in the opposite branch ofthe assembly .connected to the position-control potentiometer 21. Athird amplifier A having a reaction loop, in its turn acts on the motor16 from the potentiometric assembly 22, this amplifier being in additioninfluenced by the position of an auxiliary potentiometer 23, called thecorrection threshold, which is regulated as a function of thecharacteristics of the film emulsion being used.

The operation of the light-correction system as described above isexplained below, taking as the initial instant that when a correctionhas just been effected in the interval of a change in film sequence. Theorder for executing this correction was initiated from the input memoryM, and the delay arrangement R, by an electric pulse of l0 mS emitted bythe trigger 8,, which pulse, as explained above, operated the controlelectromagnets 10 of the three flux modulators, correspondingrespectively to the three primary colours. This same pulsesimultaneously initiates the functioning of the pulse emitter E and theadvance of the programming tape in the tape reader L. During thisadvance of the programming tape, the coded information relating to thesequence following that which is undergoing printing travel insuccession, for each of the primary colours, beneath the contacts of thetape reader L; by the co-ordinating action of the step selector S thethree memories M,, M and M are successively opened to the pulsesoriginating from the tape reader, each of these memories only retainingthe instructions relating to the fundamental colour with which it isassociated. The advance of the programming tape is ended by a fourthstep corresponding to a stopping position. Each of the three memories MM and M thus records the correction information relating to the colourin question and transmits it to the associated digital-analogueconverter C C C throughout the time necessary for the preparation of theexecution by the motor 16 and by the associated position control of thecorresponding flux modulator. Allowing for the inertia of the movingparts, this time can be in the region of 10 m8, and this, with the laggiven by R corresponds to the movement of about eight images in front ofthe projection aperture. When this time has elapsed, the three memoriesM M M; are automatically cleared by a'control circuit which is not shownin FIG. 1. At this stage of the operating cycle, the correctioninformation carried by the programming tape and relating to the sequenceto come is thus prepared by the respective flux modulators and stored.The information will be acted upon automatically with a change insequence by the control electromagnets 10 being placed under voltage inaccordance with the procedure already described, this being initiated bythe passage of the corresponding index mark of the film in front of theindex feeler of the input memory M,,.

It will be appreciated that the control system shown diagrammatically inFIG. 1 of the accompanying drawings is able, despite its relativecomplexity, to be kept within the limits of acceptable size, this beingparticularly due to the use of miniaturised elements and integratedcircuits. The flux modulators in FIGS. 2 and 3 can in their turn beeasily made in the form of units of small dimensions and reduced weight,these advantages moreover being concurrent with a desirable reduction inthe inertia of the movable components, and consequently of the responsetimes The present invention thus permits the development of a lightcorrection system which is lighter, more compact and responds morerapidly'than the mechanical control systems as known at the presenttime.

It is naturally understodd that the scope of the invention is notlimited to the preferred constructional form as described above, whichis only given by way of example, but that on the contrary it covers allmodifications in construction which make use of the same principles.

We claim:

1. A light-correction system for a cinematographic color filmprintingmachine which is adapted to operate on the additive three-colorprinciple in which the light flux emitted by a source is split up intothree monochromatic beams which are each passed through a flux modulatorand thereafter recombined, the system comprising, means for advancing aperforated programming tape on which correcting information is recordedstep-by-step with the advance of a film to be printed,

a programming tape reader for producing an output of electric pulses, adigital-analogue arrangement for converting the electric pulses intorepresentative electrical voltages; means for separately adjusting theaperture of each of the fluxmodulators, said adjusting means includingan aperture shutter and corresponding operating shaft for each fluxmodulator a separate electric motor for driving each of said adjustingmeans; separate position-controlling potentiometric assemblies forcoupling each of the motors with one of the representative voltages;means for storing correction information supplied by the reader; meansfor sensing an index mark carried by the film; means for extracting thestored information when an index mark is sensed; a cam mounted in eachof the flux modulators, for converting rotation of each correspondingmotor into an angular displacement of a pivoting member mounted forrotation on an operating shaft of an aperture shutter of the respectiveflux modulator; means for making the operating shaft fast with the saidpivoting member during a short time interval initiated by the index marksensing means; the pivoting member comprising a lever journalled at oneof the ends on the operating shaft of the corresponding aperture shutterand a blade articulated on the other end of the lever and provided atits free end with aligned lateral projections for engaging incorresponding recesses of the cam, said cam being keyed on the operatingshaft, a spring for controlling the spacing between the cam and theblade and an electromagnet for engaging the blade with the cam when thelatter receives an electric pulse indicative of a sensed index mark.

2. A light-correction system according toclaim 1, wherein the operatingshaft of the aperture shutter is hollow and in that the pivot means forthe engagement of the blade with the cam is controlled by means of asliding rod disposed coaxially of the said shaft and operated by theplunger of the electromagnet.

3; A light-correction system according to claim 2, wherein a frictionconnection is established by the action of said spring on the bladebetween the sliding rod and the hollow shaft so as to immobilise thelatter in the last angular position which was communicated to it by

1. A light-correction system for a cinematographic color film printing machine which is adapted to operate on the additive three-color principle in which the light flux emitted by a source is split up into three monochromatic beams which are each passed through a flux modulator and thereafter recombined, the system comprising, means for advancing a perforated programming tape on which correcting information is recorded step-by-step with the advance of a film to be printed, a programming tape reader for producing an output of electric pulses, a digital-analogue arrangement for converting the electric pulses into representative electrical voltages; means for separately adjusting the aperture of each of the flux modulators, said adjusting means including an aperture shutter and corresponding operating shaft for each flux modulator a separate electric motor for driving each of said adjusting means; separate positioncontrolling potentiometric assemblies for coupling each of the motors with one of the representative voltages; means for storing correction information supplied by the reader; means for sensing an index mark carried by the film; means for extracting the stored information when an index mark is sensed; a cam mounted in each of the flux modulators, for converting rotation of each corresponding motor into an angular displacement of a pivoting member mounted for rotation on an operating shaft of an aperture shutter of the respective flux modulator; means for making the operating shaft fast with the said pivoting member during a short time interval initiated by the index mark sensing means; the pivoting member comprising a lever journalled at one of the ends on the operating shaft of the corresponding aperture shutter and a blade articulated on the other end of the lever and provided at its free end with aligned lateral projections for engaging in corresponding recesses of the cam, said cam being keyed on the operating shaft, a spring for controlling the spacing between the cam and the blade and an electromagnet for engaging the blade with the cam when the latter receives an electric pulse indicative of a sensed index mark.
 2. A light-correction system according to claim 1, wherein the operating shaft of the aperture shutter is hollow and in that the pivot means for the engagement of the blade with the cam is controlled by means of a sliding rod disposed coaxially of the said shaft and operated by the plunger of the electromagnet.
 3. A light-correction system according to claim 2, wherein a friction connection is established by the action of said spring on the blade between the sliding rod and the hollow shaft so as to immobilise the latter in the last angular position which was communicated to it by the blade.
 4. A light-correction system according to claim 1, wherein each digital-analogue converter has associated with it a memory for storing information extracted from the programming tape corresponding to the respective monochromatic beam, and including single selector mechanism to switch said information to each memory with each advancing movement of the programming, the operation of the selector mechanism being initiated by the sensing of said index mark. 